Why reference values differ between countries

Differences in reference values rarely stem from disagreement about physiology. More often, it’s a matter of the reference point: the WHO sets a target for the health of the whole population, Asian countries calibrate the steps towards it against their local cuisine, and bodies such as EFSA more often describe safe ranges than single thresholds.

On top of that come differences in age groups, in the definitions of the values themselves (EAR, RDA, AI), and in the bioavailability of nutrients in the typical diet of a given region. That’s why it’s convenient to place values from two countries side by side, but they shouldn’t be subtracted from one another as if they were figures on the same scale.